This invention relates to a motor vehicle steering column having thereon an electric power assist apparatus.
A typical motor vehicle steering column includes a tubular mast jacket supported on a body of the motor vehicle, a steering shaft supported on the mast jacket for rotation about a longitudinal centerline of the mast jacket, and a steering handwheel attached to the top of the steering shaft. Manual effort applied at the steering handwheel is transferred by the steering shaft to a steering gear of the motor vehicle connected to the bottom of the steering shaft. A xe2x80x9ccolumn mountedxe2x80x9d electric power assist apparatus for supplementing the manual effort applied at the steering handwheel includes a housing rigidly attached to the bottom of the mast jacket, an electric motor supported on the housing, reduction gears in the housing for transferring the output torque of the electric motor to the steering shaft, a transducer in the housing for determining the magnitude and direction of the applied manual effort, and an electronic control for turning the electric motor on and off. For maximum structural integrity and functional reliability, it is imperative that the longitudinal centerline of the steering column be precisely aligned with a longitudinal centerline of the housing of the assist apparatus. To that end, it is known to weld an end plate to the bottom of the mast jacket, to guide the end plate to a seated position on the housing with guide pins on the housing and guide holes in the end plate, and to bolt the end to the housing. Manufacturers, however, continue to seek improved steering columns in which precise alignment of the housing of the electric power assist apparatus relative to the mast jacket is achieved reliably and at less manufacturing cost.
This invention is a new and improved motor vehicle steering column having thereon a column mounted electric power assist apparatus including a tubular mast jacket, a structural housing of the assist apparatus, a socket in an end wall of the housing consisting of an annular seat in a plane perpendicular to a longitudinal centerline of the housing and a cylindrical guide wall around the annular seat machined concentric with the longitudinal centerline of the housing, and an annular end plate rigidly attached to the bottom of the mast jacket in a plane perpendicular to a longitudinal centerline thereof having a circular edge machine concentric with the longitudinal centerline of the mast jacket after the end plate is attached. The end plate plugs into the socket and bears flush against the seat with the circular edge of the end plate fitted closely in the cylindrical guide wall of the socket so that the longitudinal centerlines of the mast jacket and the housing are precisely aligned. A C-shaped retained in an annular groove in the cylindrical guide wall overlaps the end plate to prevent dislodgement of the mast jacket from the housing, the retained has a beveled shoulder which bears on and edge of the groove and converts resilient circumferential expansion of the retainer into longitudinal thrust on the end plate against the seat of the socket thereby to eliminate lash between the end plate and the housing in the direction of the longitudinal centerlines.